| 4cy Yellow-legged Gull / Larus michahellis, Westkapelle - sea dike (The Netherlands) on 15 September 2009 |  |  |  |
A difficult individual to age, because of the possibility of a fast moulted 3cy. The most decisive features to age this one as 4cy are the complete adult-like tertials and grey coverts without any dark marking. The under-wing and the tail are also complete white. There’s a mirror on the old p10 that makes it most obvious that this primary is a third generation feather, so the new generation adult-like primaries (the most outers are not yet replaced, missing or growing) fits a 4cy much better. The dull yellowish legs and the bill pattern which show much black on the gonys are more related to a 3cy Yellow-legged Gull but not uncommon on a 4cy!
